SCOTT HORSLEY, BYLINE: Kathleen Sebelius had become a lightning rod for many of the controversies surrounding the Affordable Care Act. But on this day, at least, the storm clouds gave way to a sunny send-off in the White House Rose Garden. President Obama praised the outgoing secretary for years of service that ranged from trying to improve women and children's health to battling an outbreak of H1N1 flu.

PRESIDENT BARACK OBAMA: Of course, what Kathleen will go down in history for is serving as the Secretary of Health and Human Services when the United States of America finally declared that quality affordable health care is not a privilege, but it is a right for every single citizen of these United States of America.

HORSLEY: That effort was and is controversial, and Sebelius spoke in war-weary terms today about the long-running battle to pass the health care law, defend it in court and finally, promote its protections to a skeptical American public.

SECRETARY KATHLEEN SEBELIUS: We are on the front lines of a long overdue national change, fixing a broken health system. Now, this is the most meaningful work I've ever been a part of. In fact, it's been the cause of my life.

HORSLEY: But it's a cause that's taken a toll on Sebelius and the president.

OBAMA: She's got bumps. I've got bumps, bruises.

HORSLEY: Most bruising of all was the administration's self-inflicted blow of the now-functioning website, which ultimately forced the White House to bring in a team of outside experts.

OBAMA: Yes, we lost the first quarter of open enrollment period with the problems with healthcare.gov, and they were problems. But under Kathleen's leadership, her team at HHS turned the corner, got it fixed, got the job done and the final score speaks for itself.

HORSLEY: Ultimately, more than 7.5 million people were able to sign up for insurance on the government exchange. The president says there's still a lot more work to be done. He's nominating White House budget director Sylvia Mathews Burwell to take over from Sebelius as health secretary.

OBAMA: Sylvia is a proven manager and she knows how to deliver results. And she'll need to be a proven manager because these are tough tasks, big challenges.

HORSLEY: Some Republicans have already praised Burwell who was instrumental in negotiating a two-year budget deal. Arizona Senator John McCain called her an excellent choice. But Republicans also insist they won't drop their opposition to the Affordable Care Act just because Sebelius is stepping down. Republican Senate leader, Mitch McConnell says Obamacare has to go, too.

Administration officials say they hope to see a smooth transfer of secretaries sometime next month, but little about the health care law has ever gone smoothly, including today's send-off for Sebelius. At one point during the ceremony, the secretary looked down at the binder in front of her and discovered some of her farewell remarks had disappeared.

SEBELIUS: Unfortunately, a page is missing.

HORSLEY: Sebelius had to wing it. She pointed out that earlier this week, the president was at Lyndon Johnson's Library in Texas celebrating the 50th anniversary of the Civil Rights Act, along with some of Johnson's other domestic achievements.

SEBELIUS: And 50 years ago, my father was part of that historic Congress. He served in the Congress with the passage of Medicare and Medicaid. It seems like a wonderful passing of the baton. And the Affordable Care Act is the most significant social change in this country in that 50 year period of time.

HORSLEY: Both Sebelius and Obama hope one day the Affordable Care Act will be as much a part of the American fabric as Medicare is, and that their tenure, like Johnson's, will look better with age. Scott Horsley, NPR News, the White House. Transcript provided by NPR, Copyright NPR.